In the field of refining petroleum crude oil, a process unit called the Delayed Coker increases the yield of gasoline and other high grade products by reprocessing heavy bottom oil from one of the other process units called the Fractionator, adding value of tens of thousands of dollars per day. In the Delayed Coker process unit, the heavy oil is first passed through heaters, then passed through a special multi-port metal-seated ball-type diverter valve, called the “switch valve”, which is one application for this invention.
The switch valve diverts the flow of heated heavy oil into two large drums, or into a third drum bypass connection. The heated oil remains as liquid only for a period of time after being heated, called the “dwell” time, typically ½ to 2 hours after being heated, following which it solidifies into what is called “petroleum coke”, which is a hard form of mostly carbon. That solidification takes place in the two drums, from which the coke is removed with special equipment.
It is important that the heated oil reaches the drums before the dwell time has elapsed, so that solidification takes place there, not in the heaters, or piping, or in the switch valve. This property of heavy oil, namely conversion to solid state, presents problems in design of the switch valve, since the valve design must provide for no stagnant areas, or slow-flowing areas where heavy oil could remain longer than the dwell time. Otherwise, stagnant or near-stagnant heavy oil will convert to solid coke in such areas, and make the valve difficult or impossible to operate, or cause it to leak. Such problems can necessitate a costly shutdown of the process unit, to clean out the valve.
Some improvements of the ball valve have been attempted to resolve this problem, such as described in U.S. Pat. No. 5,181,539, which discloses having many notches that allow flow through the ball/body cavity. The one hole provided is required to be small in diameter and placed at the bottom of the drive socket. The '539 patent also requires a taper through the ball in order to induce a pressure difference that would cause flow through the ball/body cavity.
An attempt disclosed in U.S. Patent App. Pub. No. 2012/0012770 describes having small drill holes through the ball surface of a straight through valve to place the main passage in fluid communication with the plug seat in the valve body.
Similarly, U.S. Pat. No. 1,177,968 describes adding a small hole through one cheek of the ball of a straight through valve in order to drain the contents of the flow path through the ball when the valve is closed.
U.S. Pat. No. 3,036,600 adds a number of small holes near the upstream end of the ball's through passage in order to admit a small amount of fluid at the start of the ball rotation.
U.S. Pat. No. 3,270,772 includes a number of small holes in the ball valve for adding a lubricant through the outer surface of the ball into a separate chamber in the ball, not into the waterway.
U.S. Pat. No. 3,333,813 discloses a straight through ball valve with small vent holes in the ball between the waterway and the valve body to vent the ball/body cavity.
Additionally, U.S. Pat. No. 3,464,449 discloses a ball with a hole from one part of the ball's exterior surface to another part of the ball's exterior surface, and the hole does not communicate with the ball's waterway.
Furthermore, U.S. Pat. No. 5,287,889 discloses a throttling valve, not an on/off or switch valve, with a number of small holes that provide a varying number of alternative flow passages as the ball is rotated, and discharges the fluid into the outlet passage but does not cause fluid recirculation.
Other approaches to such problems have been described in U.S. Pat. Nos. 3,985,150 and 4,099,543 and in published U.S. patent application 2008/0105845.
While there have been other ball valves that added holes through balls, such as improvement attempts described above, the added holes of the example embodiments herein differ because the presently improved ball has a different shape, e.g., with a 90 degree through passage, instead of a straight through passage, therefore requiring holes in positions and shapes that have not heretofore been contemplated or described. For example, some embodiments described below use tapered (e.g., conical) flow passages through the ball into and/or from the ball-cavity space. Example embodiments generally perforate the ball so as to better use direct momentum of the main fluid flow to push fluid from the main fluid flow path into the ball/body cavity (e.g., so as to provide a relatively large volume flow that is redirected from the main fluid flow into the ball/body cavity).
Accordingly, further improvements are sought to decrease stagnation of oil around the ball and body cavity of the switch valve, and increase fluidity in the switch valve.